Numerous optical methods exist which make it possible to measure the dimensions or sizes of articles, and in particular the dimensions of the cross-section of rolled sections by measuring distances and in general angles associated with such distances. The methods of this type involve sweeping or scanning the structural shape by means of the emission field under the action of at least one deflector which is being either rotated or displaced.
The applicant has already suggested, for example, a method in which radiation is directed at the section and a portion of the radiation sent back by the section is detected by means of a detector or receiver. The cross-section is scanned by means of a rotary deflector and the radiation being sent back is kept in the observation field of the receiver by synchronizing the orientation of the emitter and receiver axes.
The results obtained by these methods have proved very satisfactory and it has thus been possible to control not only the quality of a rolled product, but also the quality of the rolling operation.
However, it is generally desirable to increase the rapidity and accuracy of these measurements both for economical reasons and effectiveness of control. In practice, the rolling speeds are increasing and to control the product being produced it is necessary to effect measurements at increasingly higher speeds. Moreover, if one wishes to produce elongate products, measurements along the product should be repeated as frequently as possible so as to better locate zones in which there is a change from correct dimensions to dimensions outside permissible tolerances.